The present invention relates to novel polyesters derived from polyethyleneglycol (hereinafter PEG) and alk(en)ylsuccinic anhydrides (hereinafter ASA) and their use as xe2x80x9cAssociation Thickenersxe2x80x9d in aqueous based coatings such as paints and printing inks. Many of these polyesters are believed to function according to the xe2x80x9cMicellar Bridgingxe2x80x9d theory.
The terms xe2x80x9cAssociation Thickenerxe2x80x9d and xe2x80x9cMicellar Bridgingxe2x80x9d are explained in U.S. Pat. No. 4,426,485 and refer to the manner by which the hydrophobic parts (hereinafter hydrophobe) of a water-soluble thickener are absorbed by a solute particle such as a latex particle to provide a network of low molecular weight thickener molecules giving good flow and levelling characteristics to water borne coatings and latex systems under high shear conditions.
Association Thickeners, including thickeners which function by Micellar Bridging theory, generally contain hydrophobes which are spaced either randomly or in clusters along a hydrophilic, especially water soluble, polymer backbone. It has now been found that polyesters which exhibit Association Thickening can be conveniently prepared by polymerising a hydroxy polyethylene alk(en)yl succinate carboxylic acid (herein after HPASCA) where the alk(en)yl hydrophobe may be distributed randomly or in clusters along the polyester backbone chain.
According to the invention there is provided a polyester of general formula 1
RO"Brketopenst"(A)(B)"Brketclosest"nCOXxe2x80x83xe2x80x831
wherein
R is hydrogen or a polymerisation terminating group;
A is the residue of poly-C2-6-alkyleneglycol containing not less than 80% by weight polyethyleneglycol;
B is the residue of C4-50-alk(en)ylsuccinic acid;
the repeat unit represented by xe2x80x94(A)(B)xe2x80x94 may be the same or different;
X is hydroxy, a group ROAxe2x80x94, a group xe2x80x94OR1, xe2x80x94NHR1 or xe2x80x94Oxe2x88x92M+;
R1 is C1-18-alk(en)yl;
M+ is a metal cation; and
n is from 2 to 100.
The Polyester Association Thickeners of formula 1 are hereinafter referred to as PAT""s.
For clarity, the residues A and B are linked via an ester group xe2x80x94Oxe2x80x94COxe2x80x94 formed between a terminal hydroxy group of the poly(C2-6-alkyleneglycol) and a carboxylic acid group of alk(en)ylsuccinic acid or its anhydride.
It is to be understood that the repeat units xe2x80x94(A)(B)xe2x80x94 of the polyester chain may contain the same or different residues A and/or the same or different residues B.
However, it is much preferred that the polyester contains different residues represented by A and/or different residues represented by B. These different residues represented by A and B may be randomly or sequentially distributed along the polyester backbone chain. It is much preferred that the residue represented by B is sequenced in the polyester backbone chain since this results in clusters of the hydrophobes which aids Micellar Bridging. This sequencing of B is readily achieved by varying the residue A.
When R is a polymerisation terminating group it is preferably C1-20-alkyl, more preferably C1-10-alkyl, even more preferably C1-6-alkyl and especially C1-4-alkyl, for example, methyl.
Preferably, R is hydrogen.
When A is the residue of a poly-C2-6-alkylene glycol containing not less than 80% by weight polyethylene glycol it is preferably a polyalkylene glycol containing ethylene oxy (EO) and propylene oxy (PO) groups. It is particularly preferred that A contains not less An than 90% and especially not less than 95% by weight polyethylene glycol.
When A contains both EO and PO groups, it is preferred that the PO groups occupy a central position in the polyether moiety i.e. EO PO EO.
When A is polyethylene glycol it may consist of two polyethylene glycol chains linked together by a linking compound via urethane or ester groups. Examples of suitable linking compounds are dicarboxylic acids or anhydrides such as succinic anhydride, maleic anhydride and phthalic anhydride or di-isocyanates such as 1,6hexane di-isocyanate and tolyl di-isocyanate.
It is much preferred, however, that A is the residue of polyethylene glycol and that the number average molecular weight of the polyethylene glycol is preferably from 200 to 35,000.
Examples of suitable polyethylene glycols are PEG 200, PEG 1500, PEG 2000, PEG 3000, PEG 4000, PEG 6000, PEG 8000, PEG 10,000 and PEG 35,000 wherein the numbers signify approximate number average molecular weight.
Preferably, the alk(en)yl group in residue B contains not greater than 30 and especially not greater than 20 carbon atoms. It is also preferred that the alk(en)yl group contains not less than 8 and especially not less than 12 carbon atoms since this aids Micellar Bridging. The alk(en)yl group may be linear or branched. Examples of alk(en)yl groups are 2-octenyl, octadecanyl, n-decyl, n-decenyl, n-tetradecyl, n-hexadecyl, n-octadecyl, dodecenyl and polyisobutylene.
Preferably, X is hydroxy or a group Oxe2x88x92M+. It is to be understood that M+ can be a monovalent, divalent or trivalent cation. When M+ represents a di-or tri-valent cation it forms a salt with two or three anions derived from the polyester of formula 1. Examples of suitable cations are ammonium, quatemary ammonium, benzalkonium, pyddinium, cetyl pyridinium, amine (primary, secondary and tertiary), alkali metal (especially sodium, potassium or lithium) and alkaline earth (especially barium, calcium and magnesium) including mixtures thereof.
Preferably, X is hydroxy.
It is preferred that n is not greater than 70, more preferably not greater than 50 and especially not greater than 30.
The number average molecular weight of the polyester of formula 1 can vary over a large range depending on the size of the hydrophobes and the length of the poly-C2-6-alkylene glycol chain residue. Nonetheless, it is preferred that the number average molecular weight does not exceed 100,000.
The acid value of the polyester of formula 1 wherein X is hydroxy is preferably less than 25, more preferably less than 15, even more preferably less than 10 and especially not greater than 5 mg KOH/g. Particularly useful thickeners have been obtained which exhibit an acid value between 0.5 and 3 mg KOH/g.
The polyesters of formula 1 may be conveniently prepared by polymerising one or more HPASCA""s of formula 2
HO(A)(B)COOHxe2x80x83xe2x80x832
wherein A and B are defined hereinbefore.
The HPASCA of formula 2 itself is obtainable by reacting a poly C2-6-alkylene glycol with an alk(en)ylsuccinic acid or preferably its anhydride (hereinafter ASA) of formula 3 in the presence of a base as catalyst and preferably in an inert atmosphere. 
wherein
R2 is C4-50-alk(en)yl which may be linear or branched.
Examples of ASA""s are 2-octen-1-ylsuccinic anhydride, octadecenylsuccinic anhydride, n-decylsuccinic anhydride, n-decenylsuccinic anhydride, n-tetradecylsuccinic anhydride, n-hexadecylsuccinic anhydride, n-octadecylsuccinic anhydride, dodecenylsuccinic anhydride and poly isobutylenesuccinic an hydrides (hereinafter PIBSA).
The ASA""s and PIBSA""s of formula 3 are well known and can be made by any processes known to the art. Some of these processes are summarised in U.S. Pat. No. 4,749,500.
The reaction between the poly C2-6-alkylene glycol and the ASA is preferably carried out at a temperature between 150 and 250xc2x0 C. and especially between 170 and 190xc2x0 C.
The base is preferably soluble in the reactants and can be a tertiary aliphatic amine, aromatic amine or pyridine derivative. Bases which are non-volatile under the reaction conditions are preferred since the equipment required does not need to be adapted to contain the base. The preferred base is 4-(N,N-dimethylamino) pyridine.
The inert atmosphere may be provided by any of the inert gases of the Periodic Table according to Mendeleev and is especially nitrogen.
The PAT""s are prepared by heating one or more HPASCA""s of formula 2 at between 180 and 200xc2x0 C. in an inert atmosphere and preferably in the presence of an esterification catalyst such as tetra-alkyl titanate, for example tetrabutyl titanate, zinc salt of an organic acid, for example zinc acetate, zirconium salt of an aliphatic alcohol, for example zirconium isopropoxide, an aromatic acid such as toluene sulphonic acid or a strong aliphatic organic acid such as haloacetic acid, for example trifluoroacetic acid. Zirconium-n-butylate is the preferred catalyst.
When the PAT is prepared from one or more HPASCA""s in a single reaction the resultant PAT consists of a polyester backbone chain wherein the hydrophobes are randomly located along the polyester chain.
However, it is also possible to sequence the hydrophobes by either polymerising one HPASCA and then reacting the resultant polymer with a different HPASCA or even a polymerised different HPASCA. This sequencing of the hydrophobes along the polyester backbone chain is an important feature of the invention since it results in clusters of the hydrophobe which aids Micellar Bridging.
Whereas it is possible to use any number of different HPASCA""s to make the PAT it has been found that there is no advantage in using more than four different HPASCA""s or homopolymers derived therefrom. Preferred PAT""s are derivable from only the two different HPASCA""s or homopolymers derived therefrom.
When the PAT contains a polymerisation terminating group R it may be conveniently prepared by reacting the final polymer containing a terminal hydroxy group with an organic moiety containing a functional group which reacts with the hydroxy group. Examples of such organic moieties are alkyl halides, di-alkylsuphates and aromatic and aliphatic carboxylic acids. When the polymerisation terminating group is alkyl, it is possible to form an alkyl end-capped HPASCA by reacting a poly C2-4-alkylene glycol mono alkyl ether with an ASA. The resultant end-capped HPASCA may then be subsequently reacted with a HPASCA containing the same or different unit AB. The use of poly C2-6-alkylene glycol mono alkyl ethers is less preferred since polymerisation is restricted to only one end of the HPASCA.
When the PAT contains the group xe2x80x94ORxe2x80x2 or xe2x80x94NHRxe2x80x2, these may be prepared under similar condition used to polymerise the HPASCA by reacting the terminal carboxylic group with an alcohol Rxe2x80x2xe2x80x94OH or an amine H2Nxe2x80x94Rxe2x80x2. When the reaction involves an amine H2Nxe2x80x94Rxe2x80x2, the esterification catalyst is not required. However, as noted hereinbefore, it is preferred that the PAT contains a terminal hydroxy group, i.e. X is hydroxy or a group xe2x80x94Oxe2x88x92Mxe2x88x92.
As noted hereinbefore the PAT""s act as Association Thickeners in aqueous formulations such as aqueous based dispersions of particulate solids, millbases, paints and printing inks including inks used in drop-on-demand printers. Many of these polymers also function by Micellar Bridging. The PAT""s can also be used to thicken aqueous dispersions and emulsions of latices, especially acrylic latices. The amount of PAT is generally less than 5%, preferably less than 3% and especially less than 1% based on the total weight of the aqueous formulation.
Thus, according to a further aspect of the invention there is provided a composition comprising water and a PAT.
There is also provided a paint or ink comprising a pigment, dispersant, water, a film-forming binder and a PAT.
The PAT may be used to thicken any aqueous or emulsion system such as aqueous coating compositions for the paper, leather and textile industries, oil well flooding compositions and drilling muds, detergents, adhesives, waxes, polishes, cosmetics and toiletries, topical pharmaceutical formulations and pesticidal or agricultural compositions for control of insects, rodents, fungi, bacteria, parasites and plant growth regulating compositions.
Toiletries includes personal care formulations which can be oil-in-water and water-in-oil formulations such as shampoos, bath gels, hair gels, hand creams, hand lotions, bath lotions, cleansing creams, hair creams and the like.
The invention is further illustrated by the following non-limiting examples whereby all references are to parts by weight unless expressed to the contrary. In these examples, the numerical value following PEG indicates the number average molecular weight of the polyethylene glycol and the length of the carbon chain attached to succinic anhydride is indicated, e.g. C18-ASA.